Drought stress due to sparse rainfall is one of the main factors determining plant species composition in semi-arid ecosystems. The tolerance of two dominant perennial grasses of northeastern Asia, Leymus chinensis and Stipa krylovii, to continuously changing drought stress was compared. Their responses to the stress were eval-uated in terms of the parameter values in Feddes model. The results indicated that transpiration in S. krylovii began to decrease at a higher matric potential (−102 cm) than in L. chinensis. L. chinensis has higher performance in tran-spiration rate at a higher matric potential. In contrast, it seemed that greater tolerance of L. chinensis for drought stress is inconsistent at lower matric potentials (−104 cm). Thus, the tolerance for drought stress was ambiguous but depended on the degree of stress. Furthermore, S. krylovii maintained a low ranspiration rate under a lower ma-tric potential, implying that this species is well-adapted to drought stress because it can continue transpiration, even under severe drought stress conditions. Notably, the es-timated values for root water uptake according to Feddes revealed strategic responses in both plants for survival in semi-arid regions.